1. Field of the Invention
The present invention relates to device and method for converting a video format of a digital T.V., and more particularly, to device and method for converting a video format of a digital T.V. which can convert an SD(Standard Definition) video into an HD(High Definition) video.
2. Discussion of the Related Art
In the GA(Grand Alliance) system proposed by the FCC(Federal Communication Committee), it has been established as a principle that a variety of video formats should be encoded or decoded. For example, there are video formats for video sources of 1080(V)*1920(H) interlaced scanning with 60 Hz field rate and of 720(V)*1280(H) progressive scanning with 24 Hz or 30 Hz frame rate in HDTV class and video formats for video sources of 480(V)*720(H) interlaced scanning with 24 Hz, 30 Hz or 60 Hz frame rate and of 480(V)*640(H) progressive scanning with 24 Hz, 30 Hz or 60 Hz frame rate in SDTV(NTSC) class. Thus, even though there are a variety of video formats which can be received, video formats displayable on a monitor are limited to one or two video formats to be consistent to performance of the monitor. And, even if an HDTV broadcasting is started, the current NTSC broadcasting will be in coexistence with the HDTV for a substantial time period. Therefore, when a display format of a digital TV is 720(V)*1280(H) progressive scanning of the HDTV class, though a video source with a 720(V)*1280(H) progressive scanning can be displayed directly, a video source with 480(V)*1280(H) interlaced scanning should be converted of its video format into 720(V)*1280(H) progressive scanning for display on the monitor. And, a frame size of an SD class video source should be enlarged as much as possible for display on an HD class frame because the SD class video source has a smaller frame size.
A background art method for converting a video format of a digital TV will be explained with reference to the attached drawings. FIGS. 1axcx9c1c illustrate the background art method for converting a video format of the SD class into the HD class in a digital TV, and FIGS. 2a and 2b illustrate an example of video format conversion in a background art digital TV in which edge pixel components in an SD class image are converted into an HD class image. For example, when a video source of an SD progressive, or interlaced scanning image is to be converted into an HD class 1920*1080 interlaced scanning image, as shown in FIGS. 1a and 1b, vertical and horizontal components of the SD class image is 1:2 up sampled, and when the video source of an SD progressive, or interlaced scanning image is to be converted into an HD class 1280*720 progressive image, the vertical and horizontal components of the SD class image is 2:3 up sampled as shown in FIG. 1c. When an SD progressive, or interlaced scanning image is up sampled and converted into an HD progressive, or interlaced image, the vertical and horizontal components of the SD image do not exhibit any distortion of the image when displayed on the monitor as an HD image.
However, edge components shown in FIG. 2a are up sampled and displayed on the digital TV monitor, the diagonal components are displayed on the monitor with an distortion as shown in FIG. 2b, because the up sampling conducted in the line doubling technique even to the edge components regardless of positions of edge pixels in the SD image causes a phenomenon as shown in FIG. 2b. The diagonal component herein is an edge component of an outline of image on a diagonal line. The diagonal component is called an edge component, hereafter. That is, the background art method for converting a video format of a digital TV has a problem in that edge components of an SD progressive, or interlaced scanning image up sampled and converted into an HD interlaced image are not exhibited on a straight diagonal line but on an irregular line, thereby displaying a distorted image.
Accordingly, the present invention is directed to device and method for converting a video format of a digital TV that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide device and method for converting a video format of a digital TV which can prevent distortion of an image.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the device for converting a video format of a digital TV having an inverse quantizer, an IDCT and motion compensator, includes a detector for detecting existence of edge components from an SD image data and providing a relevant signal accordingly, and a format convertor for interpolating and format converting an SD image data obtained by adding an SD image data from the IDCT and an SD image data from the motion compensator according to an output from the detector.
In the detection of existence of edge components, DCT coefficients of the SD image data are used.
In other aspect of the present invention, there is provided a method for converting a video format of a digital TV, including the steps of detecting existence of edge components in an SD image data from the inverse quantizer, and interpolating the SD image data by using an interpolation equation according to a result of detection in the step above, to make a format conversion of the SD image data into an HD image data.
The existence of edge components in the SD image data are determined according to a number of non-zero DCT coefficients of the inverse quantized SD image data.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.